1. Field of the Invention
This invention relates to a differential pressure measuring transducer assembly using a measuring diaphragm of semiconductor material for measuring the differential pressure between a fluid under high pressure and a fluid under low pressure and producing an electrical output when there is a difference between the two pressures being measured.
2. Description of the Prior Art
In one type of measuring diaphragm of semiconductor material, such as silicon, the diaphragm having a center area and a peripheral area of large thickness and an intermediate area of small thickness as disclosed in U.S. Pat. No. 4,135,408, for example, includes a strain producing portion disposed in the small thickness intermediate area in which a gauge resistance is provided by a dispersion method or an ion plantation method. This type of measuring diaphragm offers the advantage that substantially the same characteristics can be obtained even if the pressure is applied in different directions (whether the pressure is applied on the gauge surface or on the opposite side).
Although the gauge resistance is insulated from the measuring diaphragm of silicon by a P-N boundary, the P-N boundary has a relatively low insuration resistance. Thus it is quite difficult to prevent an electrical disturbance from outside from influencing the gauge resistance. In U.S. Pat. No. 4,135,408 referred to hereinabove, the measuring diaphragm of silicon is not electrically insulated. In the differential pressure measuring transducer assembly of this construction, it would be impossible to render the gauge resistance impervious a disturbance unless the transducer assembly as a whole is electrically insulated.